1. Field of this Invention
This invention relates to a process and equipment for the determination of the magnetite and phosphorus contents in magnetite-containing ores, either during the mining or processing of the ores.
2. Prior Art
During the mining of mineral raw materials, the composition of the raw materials must be continuously checked. This permits the determination of the percentages of gangue and ore and is often also necessary in order to minimize the content of specific undesired admixtures. Usually random samples of the raw material are taken by means of a shovel or gripping tools. The samples are then prepared for chemical analysis, e.g., they are ground and homogenized. The analysis has to be carried out so rapidly that it is thereby possible to intervene in the handling of the materials or the processing according to the result of the analysis.
As the analysis, including the sampling and processing of the sample, takes a relatively long period of time, it has so far only been possible to take samples and to intervene in the process according to the results of the analysis after much too long intervals of time. In the case of the underground mining of iron ore in a large mine, for example, this results in undesired mixing of ores having different phosphorus contents. The results of such mixing process is that the yield of ore having low phosphorus content is substantially below the theoretical yield. Mixing occurs during the actual mining process. The blasted ore is transported by bucket loaders to shafts about 40 to 200 m away. One bucket holds about 8 to 14 tons. A sample of about 1 kg is taken only from approximately every tenth bucket by means of a gripping tool. Such sample is ground, sifted and magnetically separated. Part of such sample is dried, and part of this latter amount is measured, removed and subjected to wet chemical analysis. On the basis of the result of such analysis, all further buckets handled (until the result of the next analysis is available) are tipped into the shaft for the grade of ore determined by the analysis, although as a rule the composition of the material changes from bucket to bucket. The phosphorus content, which essentially determines the quality of the ore, may fluctuate by a factor of 10 to 100.